1. Field of the Invention
The present invention relates to a battery pack in which an alarm is raised from the battery pack or an external device that is coupled with the battery pack when the battery pack over-heats and/or a build-up of pressure occurs in the battery pack.
2. Description of the Background
Recently, various studies related to rechargeable batteries have been carried out based on the technological advancement of portable electronic devices such as mobile phones, notebook computers, camcorders, and personal digital assistants (PDAs). In particular, the rechargeable batteries include Ni—Cd batteries, Pb batteries, Ni—MH batteries, Ni—Zn batteries, lithium ion batteries, lithium polymer batteries, lithium metal batteries, and zinc-air batteries. Such rechargeable batteries are combined with charging/discharging circuits, thereby forming battery packs in which charging/discharging operations are performed through terminals of the battery packs.
FIG. 1 is a block view of a conventional battery pack.
As shown in FIG. 1, the conventional battery pack includes terminals (P+ and P−), a charging/discharging field effect transistor (FET) device 12, a temperature fuse 13, a fuse 14, a battery cell 15, a primary protective circuit 16, a secondary protective circuit 17, a smart functional unit 18, and a sensor resistor 19.
In the conventional battery pack with the above structure, an external charging device or an external device is coupled with the battery pack through the terminals (P+ and P−) for charging/discharging operations. A path formed between the terminals (P+ and P−) and the battery cell 15 is referred to as a charging/discharging path through which relatively high current may flow.
For example, if the external charging device is coupled with the terminals (P+ and P−), the battery cell 15 may be charged. At this time, a charging path is formed through the terminal (P+), the charging/discharging FET device 12, the temperature fuse 13, the fuse 14, the battery cell 15 and the terminal (P−). In addition, if the external device is coupled with the terminals (P+ and P−), the battery cell 15 may be discharged. At this time, a discharge path is formed through the battery cell 15, the fuse 14, the temperature fuse 13, the charging/discharging is FET device 12, the terminal (P+), the external device, and the terminal (P−).
The battery cell 15 stores information related to a cell, such as a charge electric potential of the cell, and an amount of current flowing through the cell, and outputs the cell information to the primary and secondary protective circuits 16 and 17 and the smart functional unit 18. The primary protective circuit 16 controls the on/off operation of the charging/discharging FET device 12 depending on the cell information that is transmitted thereto from the battery cell 15. The secondary protective circuit 17 controls the operation of the fuse 14 depending on the cell information that is transmitted thereto from the battery cell 15 when the primary protective circuit 16 or the charging/discharging FET device 12 malfunction. For instance, if an excessive amount of current is applied to the battery cell 15, the secondary protective circuit 17 detects it and turns off both ends of the fuse 14, thereby shielding the excess current. The smart functional unit 18 displays the charged state of the battery cell and raises an alarm when over-charge or over-discharge occurs. The temperature fuse 13 detects the temperature of the charging/discharging FET device 12 and shuts off both ends thereof when the temperature of the charging/discharging FET device 12 exceeds a rating temperature, thereby preventing the charging/discharging FET device 12 from exploding or being burned.
Although the conventional battery pack can prevent the over-charge and over-discharge of the battery cell or the short circuit of the external device, the conventional battery pack does not raise an alarm if the temperature or pressure of the battery cell rises above the standard operating conditions due to heat that is generated in the battery cell or applied to the battery cell from external sources. For example, when the external device consumes a great amount of power or when a user enters a high-temperature room such as a sauna or a bathroom with the external device coupled with the battery pack, the temperature/pressure of the battery pack may rise suddenly. However, the conventional battery pack does not raise an alarm for the user.
If the temperature of the battery pack rises, a catalyst or an active material contained in the battery pack may dissolve and emit gases. Thus, internal pressure of the battery pack may rise suddenly, causing swelling in the battery cell and deformation of the exterior of the battery pack. In this case, the battery pack cannot be mounted on the external device. In an extreme case, the battery pack may explode or ignite while generating smoke.